1. Field of the Invention
The invention disclosed herein pertains generally to improvements in combustors or burners and more particularly relates to gas and fuel mixing for such combustors and hot air furnaces having an improved pulsing combustor.
2. Description of the Prior Art
A vast number of burner arrangements are known for a virtually limitless number of specific uses. Typically, combustion takes place in an open combustion zone with the combustion gases then passed through a heat exchanger to heat a fluid such as air or water. Conventional combustion devices are unsatisfactory since oftentimes combustion is incomplete producing various pollutants and furthermore because the efficiency obtainable from such combustion devices is relatively poor.
The known burners or combustors used for heating liquids such as water are generally quite massive and consume large amounts of fuel (usually oil or gas). Most presently used burners rely on a continuous flow of the fuel, thus perhaps wasting some of the fuel due to incomplete combustion. Combustion devices having an intermittent flow of fuel are known, for example, as in a conventional piston engine or in a pulsing combustor. Perhaps one of the first pulsing combustors was the pulse-jet engine utilized in the German V-1 rocket or buzz bomb which is described on pages 2 and 3 of the book Rocket Propulsion Elements by George P. Sutton (John Wiley & Sons, 1949.).
Another known pulsing combustor is disclosed in U.S. Pat. No. 2,857,332 to Tenney et al and is utilized in a machine for producing dispersions of liquid in air or other gases. In the Tenney et al device, a fuel-air mixture is supplied through an inlet portion of a combustor with combustion air passing sequentially through a throat of an air inlet passage and over a sloping step in a fuel injection tube. Fuel is discharged as a spray and is metered in proportion to the incoming air. The fuel-air mixture is forced through a plurality of diverging passages into a combustion zone of the combustor. The passages each have a port at the combustion chamber end of each passage. Each port is covered by a finger-like portion of a metal valve preferably made of a flexible steel. The finger-like portions of the valve are sufficiently flexible to be deflected against a backing plate by the inrush of the air-fuel mixture when the burner is operating.
Initially, the starting air-fuel mixture is introduced into the burner chamber and is ignited by a spark plug. The resulting explosion causes the finger-like portions of the valve to close against the intake ports leaving an exhaust tube as the only path of exit for the combustion zone gases. The mass of gases in the exhaust tube is then driven forceably at extremely high velocity outwardly of an open end of the exhaust tube by the expanding combustion gases produced by the explosion in the combustion zone. The rush of gases out of the exhaust tube causes a low pressure area in the combustion zone. The low pressure area induces a fresh charge of combustible air-fuel mixture through the ports and into the combustion zone. Fuel is fed to the combustion zone through a plurality of fuel ports and the air used is atmospheric air. The burner depends on the low pressure zone existing in the combustion chamber after exhaustion of the hot combustion products to induce a further flow of the air-fuel mixture into the combustion zone.
A resonant intermittent combustion heater system using a pulsing combustion arrangement similar to the pulsing combustor disclosed in U.S. Pat. No. 2,857,332 is also known in the prior art and is disclosed in U.S. Pat. No. 2,715,390, issued to Tenney et al.
A different pulsing combustion arrangement having a burner is disclosed in U.S. Pat. No. 2,959,214 issued to Durr et al. During ignition of the burner in the Durr et al device, a spark plug is activated along with a pump to supply air through a conduit under pressure to a tightly closed fuel tank. The air streaming through the tube vaporizes an amount of fuel at a diaphragm and this mixture flows into a mixing tube. The mixing tube mixes the fuel-air mixture with a further supply of air and the resulting mixture then is ignited by the spark. The burning does not provide a complete combustion of the fuel-air mixture and therefore unburned combustible components circulate within a cyclone-form combustion tube before reaching an exhaust tube. As the burner continues to operate, a part of the cyclone-form combustion tube becomes hot and the unburned combustible components which enter the cyclone combustion tube are ignited. An explosion takes place within the combustion tube and the explosion provides a sudden blast of exhaust gases through the exhaust tube. These explosions follow each other uniformly and a resonant intermittent combustion takes place providing an automatic suction of fuel and air.
A spraying device having a different pulsing combustor with an oscillating burner resonator fed by a carburetor is disclosed in U.S. Pat. No. 3,758,036 issued to Bauder et al. A blower is set into operation so that a fuel whirling chamber is pressurized via a starting air pipe and fuel is supplied to the fuel whirling chamber by a tank through a nozzle. The fuel-air mixture is then supplied through a tube to the burner and an ignition device in the burner ignites the fuel-air mixture. During subsequent operation, air is drawn into a valve chamber through a suction valve provided on a front side of the carburetor and is mixed with fuel from the fuel nozzle. On a side wall of the carburetor is a lid which carries an adjusting device for the oscillating burner resonator. The adjusting device includes an air evacuating valve associated with the fuel whirling chamber and a pressure space enclosed by the lid. A diaphragm is sealed at its edges to an outside of the lid with a middle area of the diaphragm being connected to a valve closing part of the air evacuating valve.
The Bauder et al patent also discloses a portable spraying apparatus having a hand held gun. The burner in the Bauder et al patent is cooled by air in a surrounding cooling cover which obtains the air from a blower through a pipe. An oscillating tube, also surrounded by the cooling cover, conducts the hot combustion products away from the burner toward a front section of the cooling cover. A liquid agent is introduced by the nozzle into the oscillating pipe so that the hot combustion products of the burner will turn the liquid into a steam or mist which will be expelled through a widened end section of the gun.
A known recirculating burner is disclosed in U.S. Pat. No. 3,366,154 issued to Walsh et al which shows a compact portable burner useful in flame cultivation of crops. Some of the products of combustion are recirculated from a discharge end of the burner to a position between the discharge end and a venturi throat and just forward of an oil nozzle for the purpose of providing a clean flame and more efficient burning of the fuel. A recirculation jacket surrounds a central portion of the burner and has a top wall, a bottom wall and a pair of similar symmetrically disposed side walls in a predetermined outwardly spaced relation to top, bottom and side walls of the burner. The front ends of the jacket wall and the burner wall are joined together by a front shoulder. Similarly, the rear end of the jacket wall and the burner wall are joined together by a rear shoulder. A plurality of openings is provided in the burner walls adjacent and slightly rearwardly of the front shoulder and a similar plurality of openings is provided adjacent and slightly forwardly of the rear shoulder. Hot combustion gas enters the plurality of front shoulder openings and is recirculated to the rear and reenters the burner by venturi action at the rear shoulder openings to provide a more efficient burning of the fuel as well as improved vaporization of the fuel which is preferably fuel oil.
Other patents and publications which disclose combustor arrangements of interest to the present invention include: U.S. Pat. Nos. 2,634,804 of Erickson; 2,589,566 of Neth et al; 2,077,323 of Hendrix; 2,411,675 of Alexander; 1,719,015 of Lewis; 1,885,040 of Arnold; 4,259,928 of Huber; British Pat. No. 166,455; French Pat. No. 1,366,565; and, "Pulsating Combustion: An Old Idea May Give Tomorrow's Boiler's a New Look", Power, pp. 88-91, August 1954.
Accordingly, the need exists for an improved burner which provides an efficient and economical use of fuel. Such an improved burner would have particular utility in steam generation devices and in home heating equipment especially where a fluid is to be heated by the combustion.